Fix an assertion failure in FrameSelection::selectAll().

third_party/WebKit/Source/core/editing/FrameSelection.cpp

 /*
  * Copyright (C) 2004, 2008, 2009, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 824 matching lines @@
             selectStartTarget = root.get();
     } else {
         root = selection().nonBoundaryShadowTreeRootNode();
         if (root) {
             selectStartTarget = root->shadowHost();
         } else {
             root = document->documentElement();
             selectStartTarget = document->body();
         }
     }
-    if (!root)
+    if (!root || editingIgnoresContent(root))
         return;
 
     if (selectStartTarget && !selectStartTarget->dispatchEvent(Event::createCancelableBubble(EventTypeNames::selectstart)))
         return;
 
     VisibleSelection newSelection(VisibleSelection::selectionFromContentsOfNode(root.get()));
     setSelection(newSelection);
     selectFrameElementInParentIfFullySelected();
     notifyLayoutObjectOfSelectionChange(UserTriggered);
 }
@@ skipping 555 matching lines @@
 
 void showTree(const blink::FrameSelection* sel)
 {
     if (sel)
         sel->showTreeForThis();
     else
         fprintf(stderr, "Cannot showTree for (nil) FrameSelection.\n");
 }
 
 #endif